STENUS. 661 
§ 4. Thorax very elongate, nearly cylindric; head without a definite polished elevation 
on the middle ; legs unicolorous, pallid. 
This interesting group has numerous representatives in Tropical South America, and 
also in other parts of the world. They appear to be rare insects and not met with 
gregariously. ‘The head is usually very broad, with the eyes very widely separated, and 
underneath the genz are of unusual width, so that the eyes are not visible on the 
under surface of the head; this latter character is not, however, constant, and I have 
in consequence at present included in the group some species, such as 8. sagax, which 
do not differ from the normal St¢eni in this latter respect. In the more remarkable 
species of the group the segment of the armature in the males becomes developed 
in an extraordinary manner. 
50. Stenus aculeatus. (Tab. XVII. fig. 14, 3.) 
Niger, parum nitidus; antennis, palpis pedibusque flavis; dense fortiterque punctatus ; capite lato, leviter 
excavato, plano; elytris quam prothorax paullo brevioribus. 
Long. 6 millim. 
Hab. GuatEMALA, Cerro Zunil (Champion). 
Antenne and palpi extremely elongate. Head very broad. Thorax nearly twice as 
long as broad ; very densely punctured, almost rugose. LElytra narrowing somewhat 
from the apex to the base, so that the shoulders are not very prominent ; densely and very 
coarsely punctate. Hind body coarsely punctate, the apical segments more sparingly 
than the basal. In the male the ventral plate of the armature is prolonged to form an 
elongate, very acuminate spine, the terminal segment bears a large and deep notch, 
and the preceding segment is pubescent along the middle. 
51. Stenus armatus. 
Niger, sat nitidus, elytris vix eneo-tinctis; antennis, palpis pedibusque flavis ; dense fortiterque punctatus ; 
capite lato, leviter excavato; elytris prothoracis longitudine ; abdomine fortiter punctato. 
Long. 6 millim. 
Hab. Panama, Volcan de Chiriqui 2000 to 6000 feet (Champion). 
Antenne and palpi extremely elongate. Head very broad, a little excavate, with a 
very feeble convexity along the middle. ‘Thorax nearly twice as long as broad, coarsely, 
very densely punctured, a good deal rounded at the sides. LElytra just about as long 
as the thorax, closely and extremely coarsely punctured, the shoulders moderately 
prominent. The punctuation of the apical segment definite, though finer and less dense 
than that of the basal segments. In the male the ventral plate of the armature is 
produced to form a curious laterally compressed process or lamina with rounded 
extremity, the terminal ventral plate bears a rather large notch, and the preceding 
segment is finely pubescent along the middle. 
